Life Processes

Step 1: Cellular respiration produces carbon dioxide. Step 2: Blood carries it to the lungs in different forms. Step 3: A major part is transported as bicarbonate.

Step 1: Humans need a high amount of energy. Step 2: Cells need more oxygen for more energy. Step 3: Four chambers reduce mixing of blood and improve oxygen supply.

Step 1: The first route sends blood from the heart to the lungs. Step 2: The second route sends blood from the heart to the body. Step 3: Therefore, blood passes through the heart twice in one full cycle.

Step 1: Arteries carry blood from the heart under high pressure. Step 2: So their walls are thick and strong. Step 3: Veins have low pressure, so valves prevent backflow.

Step 1: Tissues need oxygen and nutrients. Step 2: Thin capillary walls allow materials to move in and out. Step 3: A network increases contact area and speeds exchange.

Step 1: Platelets help in blood clot formation. Step 2: A clot stops bleeding at the injury site. Step 3: Low platelets increase the risk of excessive blood loss.

Step 1: Water leaves leaves as vapour. Step 2: This creates water shortage in leaf cells. Step 3: This shortage pulls water upward through xylem.

Step 1: Roots absorb water from soil. Step 2: Too much salt can make water uptake difficult for roots. Step 3: With less water, the plant may wilt.

Step 1: Sugar made in leaves is loaded into phloem. Step 2: This loading uses energy. Step 3: A pressure difference then moves food to parts that need it.

Step 1: Roots absorb water and minerals, so xylem carries them upward. Step 2: Food is made in leaves, but it may be needed anywhere. Step 3: So phloem can move food upward and downward.

Step 1: Phloem carries food made in leaves to roots. Step 2: Ring removal of bark can break the phloem path. Step 3: Roots will receive less food and their growth will be affected.

Step 1: Filtration separates wastes and small substances from blood. Step 2: The filtrate can also contain useful water, glucose, and salts. Step 3: Reabsorption returns them to blood.

Step 1: On a hot day, water loss through sweat may increase. Step 2: If less water is drunk, the body tries to conserve water. Step 3: Nephrons reabsorb more water, so urine may become concentrated.

Step 1: Protein use can produce ammonia as waste. Step 2: Ammonia is very harmful to the body. Step 3: The liver converts it into urea, which can be removed in urine.

Step 1: Dialysis uses a semipermeable membrane. Step 2: Small waste substances can pass through it. Step 3: Blood cells are large, so they remain in the blood.

Step 1: Urea is a nitrogenous waste. Step 2: Kidneys filter it from blood and remove it. Step 3: If kidneys fail, urea accumulates in blood and becomes harmful.

Step 1: Plants do not have separate excretory organs. Step 2: They can store some wastes in leaves or bark. Step 3: When old leaves fall, these wastes leave the plant.

Step 1: Nutrition provides materials in the form of food. Step 2: Cells break these materials during respiration. Step 3: This releases energy for life activities.

Step 1: Digestion changes large food molecules into small soluble substances. Step 2: Absorption moves these substances into blood. Step 3: Thus both are different but connected processes.

Step 1: Saprophytes depend on dead and decaying matter. Step 2: They release digestive juices outside to simplify complex matter. Step 3: Then they absorb the simple dissolved substances.